STANFORD (CBS 5) – One Bay Area family is celebrating a high school graduation that they never thought they would see thanks to a recent heart transplant at Stanford’s Lucile Packard Children’s Hospital.

William Wylie-Modro, a Gunn High School senior who is planning to attend UC San Diego, walked down the aisle to get his diploma Tuesday. The 17-year-old’s mother and father were in the audience.

“If you had asked me two months ago if I would be standing here with my son graduating, I would have said it was impossible. It’s amazing,” said Sheron Wylie-Modro.

Without a new heart, William might not have lived long enough to see his graduation day. He was born with a serious heart defect. A few weeks ago, the Gunn High School Senior was living on the brink of cardiac arrest when another family’s tragedy and generosity gave him another shot at life.

“I would be dead if it was not for the donor. I would have probably died last week,” said William, who doesn’t know who the donor was. “It saved my life. I’m living, breathing, beating proof that, if you click that box, you save lives.”